<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .box {
        width: 300px;
        height: 300px;
        background-color: #d5aff6;
        margin: 0 auto;
        position: relative;
        overflow: hidden;
      }
      .content {
        width: 300px;
        height: 300px;
        text-align: center;
        line-height: 300px;
      }

      .line {
        position: absolute;
      }

      .line:nth-child(1) {
        top: 0px;
        left: 0px;
        width: 100%;
        height: 5px;
        background: linear-gradient(to right, transparent, #eeff6c);
        animation: shadow1 8s linear infinite;
      }
      @keyframes shadow1 {
        0% {
          left: -100%;
        }
        50%,
        100% {
          left: 100%;
        }
      }
      .line:nth-child(2) {
        top: 0px;
        right: 0px;
        width: 5px;
        height: 100%;
        background: linear-gradient(to bottom, transparent, #6ffaff);
        animation: shadow2 8s linear infinite;
        animation-delay: 2s;
      }
      @keyframes shadow2 {
        0% {
          top: -100%;
        }
        50%,
        100% {
          top: 100%;
        }
      }
      .line:nth-child(3) {
        bottom: 0px;
        right: 0px;
        width: 100%;
        height: 5px;
        background: linear-gradient(to left, transparent, #1fde01);
        animation: shadow3 8s linear infinite;
        animation-delay: 4s;
      }
      @keyframes shadow3 {
        0% {
          right: -100%;
        }
        50%,
        100% {
          right: 100%;
        }
      }
      .line:nth-child(4) {
        bottom: 0px;
        left: 0px;
        width: 5px;
        height: 100%;
        background: linear-gradient(to top, transparent, #ff00ee);
        animation: shadow4 8s linear infinite;
        animation-delay: 6s;
      }
      @keyframes shadow4 {
        0% {
          bottom: -100%;
        }
        50%,
        100% {
          bottom: 100%;
        }
      }
    </style>
  </head>

  <body>
    <div class="box">
      <span class="line"></span>
      <span class="line"></span>
      <span class="line"></span>
      <span class="line"></span>
      <div class="content">霓虹灯</div>
    </div>
  </body>
</html>
